Table 4.

Respiratory Mechanics and Blood Oxygenation under Mechanical Ventilation

Variable	Open-lung Ventilation (n = 43)	Control Ventilation (n = 43)	P Value
Regional lung compliance,* mean ± SD, arbitrary units per cm H2O
Anesthesia onset
Ventral	176.0 ± 73.4	163.7 ± 115.6	0.639
Dorsal	123.6 ± 76.6	73.1 ± 56.6	0.005
End of surgery
Ventral	185.9 ± 96.9	167.4 ± 121.1	0.535
Dorsal	133.4 ± 111.9	89.5 ± 70.3	0.088
Respiratory system compliance, mean ± SD, ml per cm H2O
Anesthesia onset
Dynamic	67.1 ± 25.0	49.6 ± 24.3	0.015
Static	61.6 ± 16.8	45.5 ± 17.3	0.002
End of surgery
Dynamic	48.3 ± 22.6	46.5 ± 29.9	0.286
Static	53.9 ± 13.8	49.7 ± 18.7	0.119
Pao2/Fio2 ratio, mean ± SD, mmHg
Anesthesia onset	441 ± 129	311 ± 131	0.001
End of surgery	374 ± 103	273 ± 97	< 0.001
Alveolar arterial gradient, mean ± SD, mmHg
End of surgery	166 ± 81	172 ± 70	0.843
Extubation time	97 ± 48	142 ± 57	0.026

^*Measured with pulmonary electrical impedance tomography. Data come from n = 86 for respiratory system compliance and arterial oxygen tension (Pao₂)/fraction of inspired oxygen (Fio₂) ratio, n = 56 for regional lung compliance, and n = 30 for alveolar arterial gradient.